PET heat-seal film manufacturers consider polyester film to be a new type of film material, boasting excellent overall performance, high hardness and toughness, as well as outstanding puncture resistance and abrasion resistance. Consequently, polyester film is one of the most commonly used substrates for barrier composite films.

　　PET heat-seal film manufacturers note that polyester films produced via biaxial stretching undergo significant elongation in both the longitudinal and transverse directions, altering the molecular or chain‑segment orientation and subjecting the material to distinct thermal treatments during processing. As a result, their key properties are markedly modified, exhibiting the following characteristics:

　　1. The mechanical properties of the film, such as tensile strength, elongation at break, and elastic modulus, are significantly improved.

　　2. Impact strength and flexural strength are increased;

　　3. Improved aging resistance;

　　4. The refractive index increases, surface gloss improves, and film transparency is enhanced;

　　5. Increasing the width, reducing the thickness, and raising the area coefficient can improve material utilization and the uniformity of film thickness.

　　6. Improved electrical performance;

　　7. Reduced the permeation of gases such as water vapor and oxygen;

　　8. It enhances the membrane’s surface smoothness, flatness, dimensional stability, and wear resistance, while also reducing its thermal shrinkage rate.

　　PET heat-seal film manufacturers note that biaxially oriented polyester film boasts high mechanical strength, excellent optical properties, superior electrical insulation, compliance with environmental and health standards, readily available raw materials, an environmentally friendly manufacturing process, and increasingly mature processing technologies. Its applications are extremely broad. According to statistics from the DuPont Research Institute, there are nearly 2,000 different uses for polyester film. By tailoring its mechanical, optical, electrical, and thermal properties, polyester film can meet the diverse requirements of various applications.

　　PET heat-seal film manufacturers believe that the main factors influencing the haze value of the film are as follows.

　　1. The influence of additives. PET heat-seal film manufacturers note that the particle size, distribution, type, and dosage of additives significantly affect haze values. Since additives primarily function at the surface layer, a multi-layer co-extrusion process can be employed to mitigate their impact on haze within the film.

　　2. Influence of technical conditions. PET heat-seal film manufacturers note that the crystallinity of polyester film significantly affects haze values. During processing, the crystal morphology and degree of crystallinity continuously evolve, necessitating strict control. Consequently, the production line must be equipped with machinery capable of precisely regulating crystallinity. Equipment requirements include sufficient cooling capacity for the cast film, a longitudinal stretching unit that can achieve high pre‑heat temperatures without causing adhesion to the rollers, and individually driven rollers. Additionally, the horizontal stretch‑setting machine should provide an adequate thermal setting length.

　　3. The influence of raw materials. This primarily encompasses several aspects: first, the content of internal impurities, including residual catalyst; second, the material’s color tone; and third, the material’s stability.